Automatic lamp changer and spare lamp indicator circuit

ABSTRACT

A circuit for automatically energizing a spare or standby lamp in response to the burning out of the primary lamp and for continuously monitoring the spare lamp to verify operability thereof up to the time the burned-out lamp is replaced includes a source of electrical power, a relay and a two-position control switch connected such that the switch in one position connects one of the lamps in series with the power source and the relay and, in the other position connects the other of the lamps in series with the power source and the relay. A motor is actuated in response to the burning out of the primary lamp to position the control switch so that the spare lamp replaces the burned out lamp in the series circuit. The spare lamp is continuously monitored by connecting a transistorized switching network from the spare lamp to a warning or indicator lamp. The output stage of the network is switched on, thereby energizing the warning lamp, if the spare lamp is or becomes defective.

United States Patent 1 3,678,286 Willis 1451' July 18,1972

[54] AUTOMATIC LAIVIP CHANGER AND Primary Examiner-Herman J. Hohauser SPARE LAMP INDICATOR CIRCUIT Roger L. Willis, Spencerport,

Eastman Kodak Company, Rochester, NY.

March 22, 1911 lnventor:

Assignee:

Filed:

Appl. No.:

US. Cl ..307/38, 315/88, 315/90, I

Int. Cl. ..H02j l/00 Field ofSearch ..315/86, 87, 88, 89, 90, 93; 240/37, 37.1; 307/38, 39, 40, 41,11, 157

References Cited UNITED STATES PATENTS Attorney-W. H. .l. Kline and Milton S. Sales ABSTRACT A circuit for automatically energizing a spare or standby lamp in response to the burning out of the primary lamp and for continuously monitoring the spare lamp to verify operability thereof up to the time the burned-out lamp is replaced includes a source of electrical power, a relay and a two-position ,bumed out lamp in the series circuit. The spare lamp is continuously monitored by connecting a transistorized switching network from the spare lamp to a warning or indicator lamp. The output stage of the network is switched on, thereby energizing the warning lamp, if the spare lamp is or becomes defective.

4 Claims, 1 Drawing figure PATENTEDJUL 18 m2 ROGER L. W/LL l5 INVENTOR.

BY ?r. ww

A 7' TOR/VEYS AUTOMATIC LAMP CHANGER AND SPARE LAMP INDICATOR CIRCUIT BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a device for turning on a spare lamp in response to the failure of a primary lamp and for monitoring the condition of the spare lamp.

2. Description of the Prior Art In the operation of a motion picture projector adapted to record and/or reproduce sound on a strip of film having an optical sound track, the light beam from a lamp, known as an exciter lamp, is projected through the sound track of the filmstrip onto a light sensitive element, such as a photocell. The photocell, by means of suitable circuitry, then converts the light rays passing through the film toan electrical signal. Ifthe exciter lamp fails, the sound accompanying the picture is completely lost until the defective exciter lamp is replaced. A defective lamp should, therefore, be replaced as quickly as possible.

In conventional prior art devices directed to this problem, various electromechanical arrangements are utilized for the turning on of a spare exciter lamp in response to the failure of the primary exciter lamp. In such devices, a mechanism is actuated by means of an appropriate electromechanical circuit energizing the spare exciter lamp circuit. One solution of what might be termed the loss of exciter lamp" problem is described in U.S. Pat. No. 3,269,795 filed May I I, 1964 in the name of B.F. Floden. A lamp changer device described in the Floden patent includes a pair of exciter lamps mounted on a PIVUl-hr plate. A relay coil connected in series with the primary lamp controls a switch through which an electromechanical device is energized when the primary lamp fails to (l) rotate the plate, thereby physically replacing the defective lamp, (2) switch the new lamp into the circuit, and (3) energize a signal lamp to notify the projector operator that the primary exciter lamp failed. A disadvantage of the electromechanical-device disclosed in the Floden patent is that this device is operative only upon the failure of a particular one of the exciter lamps. That is, given a system comprising first and second exciter lamps, the capability exists in Floden for automatically replacing the first lamp, the primary lamp, when it fails with the second lamp, the spare lamp. However, the Floden changer must be reset by hand after the burned-out lamp is changed to prepare the changer to operate upon subsequent exciter lamp failure. In addition, no capability is provided in Floden for verifying the operability of the spare exciter lamp when the spare lamp is in the standby position.

Another prior art device for replacing a lamp upon its failure is described in US. Pat. No. 3,471,745 issued Oct. 7, 1969 in the name of CB. Meyer. The Meyer device includes apparatus for moving a spare projection lamp into projection position when a primary lamp fails. A sensing means is provided in series with both lamps to sense the current taken by the lamp that is on, and means are provided for checking the continuity of the filament of the lamp that is in the spare position. An electric motor is energized to physically exchange the lamps when less than a predetermined minimum current flows through the sensor, and means are provided for turning on the lamp which is in projecting position and for maintaining the other lamp off. While the Meyer device overcomes the abovementioned disadvantage of the Floden apparatus, it does so through the use of sophisticated and complex circuitry which would be expensive to manufacture.

SUMMARY OF THE INVENTION It is therefore,an object of the present invention to overcome the above-noted shortcomings encountered with previously known devices and toprovide an improved lamp changer which is of simple design and construction, thoroughly reliable and efficient in operation, and economical to manufacture.

A further object of the present invention is to provide a circuit of the aforementioned type wherein the operability of the spare lamp is continuously monitored to verify operability thereof.

In accordance with a preferred embodiment of the invention, an automatic lamp changer for alternatively connecting one of a pair of lamps to an electrical source. The changer includes switch means conditionable between a first state connecting only one of the lamps in series with the source and a second state connecting the only other of the lamps in series with the source. Means responsiveto the switch means being in its first and second state upon the failure .of a lamp are provided for conditioning the switch to its second and first state, respectively.

Other features and advantages of the invention will be set forth in or apparent from the detailed description of a presently preferred embodiment thereof found hereinbelow.

BRIEF DESCRIPTION OF THE DRAWING In the detailed description of the preferred embodiment of the invention presented below, reference is made to the accompanying drawing, which is schematic circuit diagram of the lamp changer and spare lamp continuity indicator according to the preferred embodiment of the present invention.

DESCRIPTION or PREFERRED EMBODIMENT As stated hereinbefore, the present invention relates to a device for turning on a spare lamp in response to the failure of a primary lamp and for monitoring the condition of the Spare lamp. Such devices have various uses such as for example in conjunction with automobile lights, warning lights of many types, still and cine projection lamps, exciter lamps for optical sound transducers, and many other situations where it would be dangerous or inconvenient to experience a lamp failure without an immediate and automatic replacement of the failed lamp. In the present description of the invention, it will be assumed by way of example that the apparatus is intended for use in conjunction with the exciter lamps of a sound motion picture projector.

Because sound projectors are well known, the present description will be directed in particular to elements forming part of, or cooperating more directly with elements in accordance with the present invention. It is to be understood that projector elements not specifically shown or described may take various forms well known to those skilled in the art.

Referring to the drawing, there is shown, enclosed within the dash lines, an exciter lamp changer circuit generally denoted l0 and, enclosed within the dot-dash lines, a spare exciter lamp continuity indicator circuit generally denoted 12. As shown in the schematic drawing, there are two exciter lamps, a lamp 26 and a lamp 27. The exciter lamp connected in series with a relay 16 will be referred to herein as the primary exciter lamp; that is, the lamp whose light beam is used to retrieve sound from the sound track of the film, the remaining exciter lamp serving as the spare or back-up lamp. In the circuit configuration illustrated, lamp 27 is the primary exciter lamp, and lamp 26 is the spare exciter lamp. As stated, the overall circuit operates regardless of which lamps 26 or 27 is the primary lamp.

The lamp changer circuit 10 includes a terminal 14 connected to a suitable source of DC potential 14. Circuit 10 includes relay 16, having an operating coil 17 interconnecting terminal 14 and a two-position snap-action switch 18. Switch 18 includes a switch arm 19 movable between a. first, de-actuated position in which contact is made with a normally closed terminal ,21 and a second, actuated position in which contact is made with a normally open terminal 20. In the first position thereof, switch 18 is conditioned to connect relay 16 in series with lamp 27 whereas in the second position thereof, switch 18 is conditioned to connect relay 16 in series with lamp 26. Lamp 26 is connected to a first, normally closed contact 25 of a two-position snap-action switch 22 which further includes a switch arm 23 and a second, normally open contact 24. When arm 23 engages contact 24, lamp 27 is connected in series with switch 22, and when the arm engages contact 25, lamp 26 is connected in series with that switch.

A potentiometer 28 is connected in parallel across relay 16. The resistance of potentiometer 28 may be adjusted to regulate the voltage dropped across the exciter lamp connected in series with relay 16 to vary the lamps intensity by moving a tap 28a.

Lamp changer circuit also includes a circuit having an alternating current power supply 31 and an AC motor 30 having an output drive shaft 32. Relay 16, described above, controls operation of normally closed contacts 34 and normally open contact 35 in the AC circuit. When relay 16 is energized, by current flowing through coil 17, contacts 35 are closed and contacts 34 are opened. When relay 16 is de-energized, contacts 35 open and contacts 34 close. As shown in the schematic circuit diagram, when contacts 34 are closed, a source of AC potential is applied across a motor 30.

A two-position snap-action switch 40, which includes an arm 41, is normally connected to a terminal 42 but will be moved by a cam 380 into engagement with a terminal 42. The cam 38 is mounted on a shaft 32 which is rotated when the motor 30 is energized. Terminal 42 is connected to a point on a connection between supply 31 and normally closed contacts 34 of relay 16. Tem1inal 43 is connected at the electrical junction between the cathode of a diode 44 and the positive plate of a capacitor 45. The anode of the diode 44 is connected to the junction between contacts 35 and the arm 41 of switch 40. The capacitor 45 is connected between AC source 31 and motor 30.

Mounted on shaft 32 is a mechanical switching assembly consisting of substantially identically constructed cams'38a, 38b engaging switch arms 19 and 23 respectively, and a cam 38c engaging switch arm 41. The construction of the switching assembly plays an important part in actuating the switches for controlling the energization of the spare exciter lamp in response to failure of the primary exciter lamp. Although the switching assembly is shown as consisting of three distinct cams, it will be understood that the assembly may be constructed as a single unit or may take other suitable forms not inconsistent with the teaching of this invention.

Switching assembly 38 is constructed so that when the primary exciter lamp fails, the spare exciter lamp can be switched into operation as rapidly and reliably as possible. In providing rapid substitution of the defective lamp with the spare, operable lamp, care must be taken to prevent overtravel of cams 38a and 38b so that reliable electrical conduction through switch arms 19 and 23 to the lamps is maintained. Substitution of the defective lamp with the spare lamp is achieved when cams 38a and 38b rotate to cause arms 19 and 23, respectively, to change positions. In a preferred embodiment, the shape of cams 38a and 38b when viewed axially along shaft 32 is that of a half circle, (the drawing having been somewhat distorted to show this feature). When the curved portion of the outer surface of cam 38a engages arm 19, the arm is caused to travel from contact 21 to contact 20. Likewise, the curved portion of cam 38b engaging arm 23 will cause this arm to travel from contact 25 to contact 24 of switch 22. When the switch arms travel in this direction, lamp 26 becomes the primary lamp and lamp 27 becomes the spare lamp. When the flat portion of cams 38a and 38b is rotated toward arms 19 and 23 respectively the arms are free to return to and engage contacts 21 and 25. When this happens, lamp 27 is again the primary lamp and lamp 26 is again the spare lamp. Because of the half-circle shape of cams 38a and 38b, the defective lamp may be substituted with the spare, operable lamp within a one-half revolution of shaft 32. If desired, the physical positions of lamps 26 and 27 may be changed by energization of motor 30 to align whichever lamp is lighted with the sound transducer. One method of shifting the lamp positions is shown in aforementioned U.S. Pat. No. 3,471,745 to CB. Meyer.

Cam 38c is constructed such that within the time carts 38a and 38b are causing switches 18 and 22 to change a single position, i.e., within a one-half revolution of shaft 32, cam 380 is causing arm 41 of switch 40 to travel from contact 43 to contact 42 and then back to contact 43.

Exciter lamp continuity circuit 12 generally comprises a two-stage transistorized switching network. A transistor 52 of the first stage has its emitter electrode connected in series to the spare exciter lamp, which in the configuration shown is lamp 26 and a transistor 54 of the second stage which has its emitter electrode connected to a warning lamp 56 which may be located within the operators view. A resistor 53 which is connected between a terminal 50 of a direct current power source, and the base electrode of transistor 52 serves to regulate the potential for both transistors 52 and 54. More specifically, the collector electrode of transistor 52 is connected to terminal 50 through a resistor 55 and the base electrode is connected to DC source 50 through a resistor 53. The collector electrode of transistor 54 is connected through a lamp 58 to terminal 50, whereas the base electrode of transistor 54 is directly coupled to the collector electrode of transistor 52, (viz. in a common-emitter configuration). Emitter electrode of the transistor 54 is connected through a switch 58 to ground potential. Switch 58, when closed, enables power to be applied to continuity circuit 12 and lamp changer circuit 10.

OPERATION With the circuit in the configuration shown in the schematic drawing, exciter lamp 27 will be lighted when switch 58 is 7 closed, and the current passing through that lamp will energize relay 16, thereby opening contacts 34 and disconnecting AC power source 31 from motor 30. The motor 30 being unenergized, switches 18, 22 and 40 remain in the positions shown.

With switch 58 closed, power is also applied to the spare exciter lamp continuity indicator circuit 12 through terminal 50. If the spare exciter lamp, lamp 26, is operable, transistor 52 will turn on causing current to flow from terminal 50 through the circuit consisting primarily of resistor 55, the collector-emitter junction of transistor 52, switch 22 and the spare lamp. The voltage at junction A of continuity indicator circuit 12 is equal to the voltage at terminal 50 less the voltage dropped across the resistor 55. When transistor 52 is on, and hence, the spare exciter lamp is operable, the voltage at junction A is not sufficiently high to gate transistor 54 on. When transistor 54 is off, warning light 56 remains off, thereby indicating the spare exciter lamp is operable.

Iflamp 27, the primary exciter lamp in the illustrated circuit configuration, burns out, the circuit comprising relay 16, and lamp 27 is broken, de-energizing relay 16. With relay 16 deenergized, contacts 34 close thereby applying AC potential across motor 30. When motor 30 is energized, shaft 32 rotates and effects a like rotation of cams 38a, 38b and 38c.

As described hereinabove, cams 38a, and 38b when rotated will cause switch arms 19 an 23, respectively to change a single position whereas cam 38c will cause switch arm 41 to travel from contact 43 to contact 42 and back to contact 43. Assuming that lamp 27 has been the primary lamp, its failure will cause arms 19 and 23 to be actuated to engage contacts 20 and 24, respectively (if lamp 26 has been the primary exciter lamp upon failure thereof, arms 19 and 23 would be de-actuated to travel from contacts 20 and 24 to contacts 21 and 25, respectively). VVlth arm 19 engaging contact 20, lamp 26 is connected in series to relay 16, and as such as in the primary lamp position. Likewise, lamp 27 is connected in series through switch 22 to transistor 52, and is in the spare lamp position.

While switches 18 and 22 are switching positions, arm 41, actuated by cam 38c, briefly engages contact 42. When this happens a circuit is temporarily established from source 31 through switch 40, diode 44, and capacitor 45. During this brief time, capacitor 45 charges to a magnitude of voltage proportional to the value of the positive half wave of the AC signal generated by source 31. Arm 41 then returns to contact 43 just before the interchange of lamps 26 and 27 is completed. When lamp 26 is connected in series to relay 16, the relay is energized and contact 35 is closed and contact 34 is opened. With contact 35 closed, a circuit is completed from the positive plate of capacitor 45 through switch 40, contact 35 and motor 30 to the negative plate of the capacitor. This circuit, which is established at the time relay 16 is energized and, hence, at the time source 31 is disconnected from the motor 30 due to the opening of contact 34, pemiits the voltage stored on the positive plate of the capacitor 35 to discharge in the windings of the motor. The discharging of the capacitor voltage in motor 30 acts to rapidly brake shaft 32 to prevent undesirable overtravel of cam assembly 38 once the arms of switches 18, 22 and 40 have reached their desired positions.

As hereinbefore mentioned, the burned-out lamp, lamp 27, is at this time switched into a series connection with the emitter electrode of transistor 52. Lamp 27, being inoperative, causes transistor 52 to turn off. With transistor 52 off, the voltage at junction A rises, so that transistor 54 is turned on, and current flowing through transistor 54 lights lamp 56 to signal the projector operator that lamp 27 has failed.

From the above, it will be understood that the overall circuit is operative when either exciter lamp is acting as the primary exciter lamp. That is, it is not necessary, once the burned-out lamp has been replace, to reset the circuit to the original configuration in that the lamp previously serving as the spare lamp now acts as the primary lamp. By simply manually replacing the burned-out lamp, the overall circuit is operative to respond to the next primary lamp failure.

The invention has been described in detail with particular reference to a preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

1 claim:

1. An automatic lamp changer for alternatively connecting one of a pair of lamps in series with a first source of electrical energy, said lamp changer comprising:

switch means conditionable between (1) a first state connecting only one of said pair of lamps in series with said first source and (2) a second state connecting only the other of said pair of lamps in series with said first source; an electro-mechanical device having an output;

means interconnecting said output and said switch means for changing the state of said switch means upon energization of said electro-mechanical device;

a second source of electrical energy; and

means l) responsive to said switch means being in said first state upon the failure of said one lamp for interconnecting said electro-mechanical device and said second source for conditioning said switch means to said second state and (2) responsive to said switch means being in said second state upon the failure of said other lamp for interconnecting said electromechanical device and said second source for conditioning said switch means to said first state.

2. An automatic lamp changer connecting one of a pair of lamps in series with a source of electrical energy, said lamp changer comprising:

a relay having an inductive coil;

a switch means conditionable between (1) a first state connecting one of said pair of lamps in series with said source and said coil and (2) a second state connecting the other of said pair of lamps in series with said source and said coil;

an electric motor having an output;

means interconnecting said motor output and said switch means for conditioning said switch means to its second state upon energization of said motor when said switch means is in its first state, and for conditioning said switch means to its first state upon energization of said motor when said switch means is in its second state; and a second source of electrical energy, said relay being effective upon the lack of current through said coil to connect said second source over said motor and upon the presence of current through said coil to disconnect said second source from said motor.

3. An automatic lamp changer as defined in claim 2 further comprising:

means for sensing the condition of the lamp not connected in series with said first mentioned source and for detecting the failure of such lamp; and

means responsive to the detection of a failed lamp by said sensing means for indicating the failure of such lamp.

4. An automatic lamp changer as defined in claim 3 wherein:

said indicating means includes (1) a third source of electrical energy, (2) a signal device, and (3) normally open switch means in series with said third source and said signal device; and

said sensing means includes (1) means for detecting the continuity of the lamp not connected in series with said first mentioned source, and (2) means for closing said normally open switch means in response to the detection of the noncontinuity of such lamp. 

1. An automatic lamp changer for alternatively connecting one of a pair of lamps in series with a first source of electrical energy, said lamp changer comprising: switch means conditionable between (1) a first state connecting only one of said pair of lamps in series with said first source and (2) a second state connecting only the other of said pair of lamps in series with said first source; an electro-mechanical device having an output; means interconnecting said output and said switch means for changing the state of said switch means upon energization of said electro-mechanical device; a second source of electrical energy; and means (1) responsive to said switch means being in said first state upon the failure of said one lamp for interconnecting said electro-mechanical device and said second source for conditioning said switch means to said second state and (2) responsive to said switch means being in said second state upon the failure of said other lamp for interconnecting said electromechanical device and said second source for conditioning said switch means to said first state.
 2. An automatic lamp changer connecting one of a pair of lamps in series with a source of electrical energy, said lamp changer comprising: a relay having an inductive coil; a switch means conditionable between (1) a first state connecting one of said pair of lamps in series with said source and said coil and (2) a second state connecting the other of said pair of lamps in series with said source and said coil; an electric motor having an output; means interconnecting said motor output and said switch means for conditioning said switch means to its second state upon energization of said motor when said switch means is in its first state, and for conditioning said switch means to its first state upon energization of said motor when said switch means is in its second state; and a second source of electrical energy, said relay being effective upon the lack of current through said coil to connect said second source over said motor and upon the presence of current through said coil to disconnect said second source from said motor.
 3. An automatic lamp changer as defined in claim 2 further comprising: means for sensing the condition of the lamp not connected in series with said first mentioned source and for detecting the failure of such lamp; and means responsive to the detection of a failed lamp by said sensing means for indicating the failure of such lamp.
 4. An automatic lamp changer as defined in claim 3 wherein: said indicating means includes (1) a third source of electrical energy, (2) a signal device, and (3) normally open switch means in series with said third source and said signal device; and said sensing means includes (1) means for detecting the continuity of the lamp not connected in series with said first mentioned source, and (2) means for closing said normally open switch means in response to the detection of the noncontinuity of such lamp. 